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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

15983 results found.

  1. GRB 251205A: NOT optical observations
  2. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  3. Swift GRB 251205A : MASTER OT detection with host galaxy
  4. GRB 251205A: Swift detection of a burst with an optical afterglow
  5. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  6. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  7. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  8. GRB 251202A: SVOM/GRM observation
  9. GRB 251203A: SVOM/GRM observation
  10. GRB 251201B: SALT spectroscopic redshift z = 1.599
  11. GRB 251203C: J-band observations with WINTER
  12. EP251130a: JinShan near-infrared observations
  13. GRB 251203C: LCO optical afterglow confirmation
  14. GRB 251203C: SVOM/VT optical counterpart
  15. GRB 251203C: LCO optical upper limits
  16. GRB 251203B: LCO optical upper limits
  17. GRB 251203B: SVOM/VT optical observation
  18. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  19. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  20. EP251130a: MAO/AZT-22 optical observations
  21. GRB 251202A / EP251202a: SVOM/VT optical observation
  22. EP251202a/GRB 251202A: KAIT optical observations
  23. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  24. GRB251129A/EP251129a: Swift UVOT detection
  25. GRB 251201B: Kilonova-Catcher optical afterglow detection
  26. EP251130a: continued NOT optical observations indicate steep fading phase
  27. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  28. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  29. GRB 251202A: GOTO optical afterglow detection
  30. GRB 251126A: SAO RAS optical marginal detection
  31. GRB 251202A: Swift-XRT afterglow detection
  32. EP251129a/GRB 251129A: NOWT Detection
  33. GRB 251126A: SVOM/VT optical observation
  34. EP251130a: SVOM/VT optical observation
  35. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  36. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  37. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  38. GRB 251201A: SVOM/GRM observation of a burst
  39. GRB 251201B: SVOM/VT optical fading
  40. Swift GRB 251201B : MASTER optical counterpart detection
  41. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  42. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  43. GRB 251201B: Swift detection of a burst with an optical counterpart
  44. EP251130a: Mondy optical observations
  45. EP251130a: Optical detections with Kinder observations
  46. EP251130a: SAO RAS optical observations
  47. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  48. EP251130a: KAIT optical observations
  49. EP251130A: Optical observation from 1.3m DFOT
  50. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  51. EP251130a: JinShan optical observations
  52. GRB 251127A: SVOM/GRM observation
  53. EP251130a: Swift-XRT counterpart detection
  54. EP251130a: COLIBRÍ optical counterpart candidate
  55. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  56. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  57. GRB 251129A / EP251129a: SAO RAS optical observations
  58. GRB 251126A: SAO RAS optical observations
  59. GRB 251128A: SVOM/GRM observation of a long burst
  60. SVOM GRB 251129A : MASTER optical counterpart detection
  61. GRB 251129A: Swift-XRT afterglow detection
  62. GRB 251129A / EP251129a: SVOM/VT optical fading
  63. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  64. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  65. GRB 251129A: Correction to the position of the optical counterpar
  66. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  67. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  68. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  69. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  70. GRB 251126A: further SAO RAS optical observations
  71. GRB 251126A NUTTelA-TAO Early Measurements
  72. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  73. GRB251126A: MAO/AZT-22 optical observations
  74. GRB251126A: Continued optical observation from 1.3m DFOT
  75. GRB 251126A: Swift/UVOT Detection
  76. EP251124a: Pan-STARRS ri-band imaging and photometry
  77. GRB 251126A: Mondy and SAO RAS optical observations
  78. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  79. GRB 251126A: NOT optical observations
  80. GRB 251126A: 1.3m DFOT optical afterglow detection
  81. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  82. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  83. GRB 251126A: Kilonova-Catcher optical afterglow detection
  84. GRB 251126A: Asiago i-band detection
  85. GRB 251126A: Nanshan/HMT optical afterglow detection
  86. GRB 251126A: GIT discovery of the likely optical afterglow
  87. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  88. EP251124b: NOT r- and z-band optical upper limits
  89. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  90. EP251124a: Xinglong GWAC-F60A optical observation
  91. EP251124a: NOT r- and z-band optical upper limits
  92. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  93. EP251124a: Optical upper limit with Kinder observations
  94. EP251118A: 6 GHz VLA Detection
  95. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  96. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  97. EP251124a: GROWTH-India Telescope optical upper limits
  98. GRB 251122A/EP251122a: FTW optical and NIR observations
  99. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  100. GRB 251122A / EP251122a: Xinglong 2.16m optical observation

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